Multipurpose Sensor Port

ABSTRACT

A sensor port is adapted to connect to either a sensor or a data source. A reader is configured to identify which of the sensor and the data source is connected to the sensor port. A data path is configured to communicate an analog signal associated with the sensor and digital data associated with the data source to a signal processor according to the identification made by the reader.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/898,680,entitled “Multipurpose Sensor Port,” filed Jul. 23, 2004, andapplication Ser. No. 10/898,680 claims the benefit of U.S. ProvisionalApplication No. 60/490,091 filed Jul. 25, 2003, entitled “MultipurposeSensor Port.” The present application incorporates the disclosure ofboth of the foregoing applications herein by reference.

BACKGROUND OF THE INVENTION

A pulse oximeter is a physiological instrument that provides noninvasivemeasurements of arterial oxygen saturation along with pulse rate. Tomake these measurements, a pulse oximeter performs a spectral analysisof the pulsatile component of arterial blood so as to determine therelative concentration of oxygenated hemoglobin, the major oxygencarrying constituent of blood. Pulse oximeters provide early detectionof decreases in the arterial oxygen supply, reducing the risk ofaccidental death and injury. As a result, these instruments have gainedrapid acceptance in a wide variety of medical applications, includingsurgical wards, intensive care units, general wards and home care.

FIG. 1 illustrates a pulse oximetry system 100 having a sensor 110 and amonitor 120. The monitor 120 may be a multi-parameter patient monitor ora standalone, portable or handheld pulse oximeter. Further, the monitor120 may be a pulse oximeter 200, such as an OEM printed circuit board(PCB), integrated with a host instrument including a host processor 122,as shown. The sensor 110 attaches to a patient and receives drivecurrent from, and provides physiological signals to, the pulse oximeter200. An external computer (PC) 130 may be used to communicate with thepulse oximeter 200 via the host processor 122. In particular, the PC 130can be used to download firmware updates to the pulse oximeter 200 viathe host processor 122, as described below.

FIG. 2 illustrates further detail of the pulse oximetry system 100. Thesensor 110 has emitters 112 and a detector 114. The emitters 112typically consist of a red light emitting diode (LED) and an infraredLED that project light through blood vessels and capillaries underneatha tissue site, such as a fingernail bed. The detector 114 is typically aphotodiode positioned opposite the LEDs so as to detect the emittedlight as it emerges from the tissue site. A pulse oximetry sensor isdescribed in U.S. Pat. No. 6,088,607 entitled “Low Noise Optical Probe,”which is assigned to Masimo Corporation, Irvine, Calif. and incorporatedby reference herein.

As shown in FIG. 2, the pulse oximeter 200 has a preamp 220, signalconditioning 230, an analog-to-digital converter (ADC) 240, a digitalsignal processor (DSP) 250, a drive controller 260 and LED drivers 270.The drivers 270 alternately activate the emitters 112 as determined bythe controller 260. The preamp 220, signal conditioning 230 and ADC 240provide an analog front-end that amplifies, filters and digitizes thecurrent generated by the detector 114, which is proportional to theintensity of the light detected after tissue absorption in response tothe emitters 112. The DSP 250 inputs the digitized, conditioned detectorsignal 242 and determines oxygen saturation, which is based upon thedifferential absorption by arterial blood of the two wavelengthsprojected by the emitters 112. Specifically, a ratio of detected red andinfrared intensities is calculated by the DSP 250, and arterial oxygensaturation values are empirically determined based upon the ratioobtained. Oxygen saturation and calculated pulse rate values arecommunicated to the host processor 122 for display by the monitor 120(FIG. 1). A pulse oximeter is described in U.S. Pat. No. 6,236,872entitled “Signal Processing Apparatus,” which is assigned to MasimoCorporation, Irvine, Calif. and incorporated by reference herein.

Further shown in FIG. 2, the pulse oximeter 200 has a sensor port 210and a communications port 280. The sensor port 210 includes a connectorand associated input and output signals and provides an analogconnection to the sensor 110. In particular, the sensor port 210transmits a drive signal 212 to the LED emitters 112 from the LEDdrivers 270 and receives a physiological signal 214 from the photodiodedetector 114 in response to the LED emitters 112, as described above.The communication port 280 also includes a connector and associatedinput and output signals and provides a bi-directional communicationpath 282 between the pulse oximeter 200 and the host processor 122. Thecommunication path 282 allows the DSP 250 to transmit oxygen saturationand pulse rate values to the monitor 120 (FIG. 1), as described above.The communication path 282 also allows the DSP firmware to be updated,as described below.

Additionally shown in FIG. 2, the pulse oximeter 200 has amicro-controller 290 and a flash memory 255. The flash memory 255 holdsthe stored program or firmware that executes on the DSP 250 to computeoxygen saturation and pulse rate. The micro-controller 290 controls datatransfers between the DSP 250 and the host processor 122. In particular,to update the DSP firmware, the firmware is uploaded into the PC 130(FIG. 1), which downloads the firmware to the host processor 122. Inturn, the host processor 122 downloads the firmware to themicro-controller 290, which downloads it to the DSP 250. Finally, theDSP 250 writes the firmware to the flash memory 255.

SUMMARY OF THE INVENTION

To update the firmware in a pulse oximeter, particularly firmware on anOEM PCB integrated into a host instrument, requires a circuitous pathusing multiple protocols and multiple processors developed by differentcompanies. Some of the protocols and processor interfaces arenon-standard, requiring custom programming for different instruments.This is particularly problematic when the instruments are part of aninstalled base at various medical facilities. Further, some pulseoximeter products, such as handheld products, may not have acommunications port for connecting to an external computer, and firmwareupgrades would typically require returning the instrument to thefactory.

Every pulse oximeter has a sensor port, which provides access to a DSPvia one or more signal paths. Therefore, it is desirable to utilize asensor port for downloading pulse oximetry firmware to the DSP. It isalso desirable to provide this sensor port capability in existinginstruments without hardware modification. Utilizing a sensor port inthis manner would alleviate an instrument manufacturer from having toprovide download communication capability between a host processor andan OEM PCB and would allow easy field upgrades of all instruments,including handhelds.

One aspect of a multipurpose sensor port is a physiological measurementmethod comprising a sensor port adapted to connect with an analogsensor, and a digital data source connected to the sensor port. Anidentifier associated with said data source is read, where theidentifier is indicative that the data source is connected to the sensorport in lieu of the analog sensor. Digital data is then received overthe sensor port. In one embodiment, the digital data is compiled in asignal processor. Where the digital data are instructions executable bythe signal processor, the data may then be written from the signalprocessor into a firmware memory. The instructions may be uploaded to aPC, which is attached to a PC interface that is attached to the sensorport. Alternatively, the instructions are stored into a nonvolatilememory that is in communications with the sensor port. In anotherembodiment, the digital data is processed as a physiological signal.

Another aspect of a multipurpose sensor port is a physiologicalmeasurement system having a sensor port adapted to connect to a sensorand a data source. A reader is configured to identify which of thesensor and the data source is connected to the sensor port. A data pathis configured to communicate an analog signal associated with the sensorand digital data associated with the data source to a signal processoraccording to the reader. In one embodiment, a firmware memory isconfigured to provide instructions to the signal processor. The signalprocessor is programmed to download the instructions from the datasource and store the instructions in the memory. The instructions areexecutable by the signal processor so as to extract a physiologicalmeasurement from the analog signal. The data source may be a PCinterfaced to the sensor port, where the instructions are uploaded tothe PC. Alternatively, the data source is a nonvolatile memory adaptedto communicate with the sensor port, where the instructions being storedin a nonvolatile memory.

In another embodiment, a first physiological measurement is derivable bythe signal processor from the analog signal, and a second physiologicalmeasurement is derivable by the signal processor from the digital data.In yet another embodiment, a drive path is configured to communicatestored data associated with a physiological measurement to a digitaldevice connected to the sensor port. The stored data may be trend dataand/or log data maintained in memory that can be accessed by the signalprocessor. In a further embodiment, a drive path is configured tocommunicate acknowledgement data in conjunction with the communicationof the digital data.

Yet another aspect of a multipurpose sensor port is a physiologicalmeasurement method where a drive path is provided that is adapted toactivate emitters so as to transmit optical radiation through a fleshymedium having flowing blood. A signal path is provided that is adaptedto communicate a detector response to the optical radiation afterattenuation by the fleshy medium, where the response is indicative ofoptical characteristics of the flowing blood. Output digital data istransmitted over at least a portion of the drive path. In oneembodiment, the output digital data is read from a memory having trenddata and/or log data. In another embodiment, input digital data isreceived over at least a portion of the signal path, and receipt of thatinput digital data is acknowledged with the output digital data. In aparticular embodiment, the input digital data is stored for use assignal processing instructions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general block diagram of a prior art pulse oximeter systemutilizing an OEM printed circuit board (PCB);

FIG. 2 is a detailed block diagram of a prior art pulse oximeter system;

FIGS. 3A-D are general block diagrams of a multipurpose sensor portconnected to an analog sensor, a digital data source, or both;

FIG. 4 is a general block diagram of a multipurpose sensor port havingvarious digital data source inputs;

FIG. 5 is a block diagram of a multipurpose sensor port configured todownload pulse oximeter firmware;

FIG. 6 is a DSP firmware memory map;

FIG. 7 is a detailed block diagram of a multipurpose sensor portembodiment and associated signal and data paths;

FIG. 8 is a flowchart of a digital data receiver routine; and

FIG. 9 is a schematic of a RS232 interface for a multipurpose sensorport.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Overview

FIGS. 3A-B illustrate a pulse oximeter 300 having a multipurpose sensorport 301 connected to an analog sensor 310 and a digital data source320, respectively. As shown in FIG. 3A, if the pulse oximeter 300determines that an analog sensor 310 is attached to the multipurposesensor port 301, the multipurpose sensor port 301 is operated in ananalog mode and functions as a typical sensor port, described above. Asshown in FIG. 3B, if the pulse oximeter 300 determines that a digitaldata source 320 is attached to the multipurpose sensor port 301, themultipurpose sensor port 301 is operated in a digital mode and functionsas a digital communications device. The data source 320 may connect to asensor port interface 330 which, in turn, connects to the sensor port301. The sensor port interface 330 may be used, for example, to presenta standard communications interface, such as RS-232, to the data source320. In one embodiment, when the pulse oximeter 300 is powered up, itreads an information element or other means of identification (ID) forthe device connected to the sensor port 301. The ID identifies thedevice as either an analog sensor 310 or a data source 320. A sensorinformation element is described in U.S. Pat. No. 6,397,091 entitled“Manual and Automatic Probe Calibration,” which is assigned to MasimoCorporation, Irvine, Calif. and incorporated by reference herein.

FIG. 3C illustrates a sensor port embodiment where a resistor value is adevice ID. A resistor 303 is located in a device 302, which includes asensor 310 (FIG. 3A), data source 320 (FIG. 3B) or interface 330 (FIG.3B). The sensor port 301 has a reader 304 that measures the resistorvalue. The reader 304 includes a voltage source 305 and a currentmeasurement device 307, such as a current-to-voltage converter. Thevoltage source 305 has a known voltage, which is applied to the resistor303 when the device 302 is connected to the sensor port 301. The currentmeasurement device 307 senses the magnitude of the resulting currentflowing through the resistor 303 so as to determine the resistor valueand, hence, the device ID.

FIG. 3D illustrates a pulse oximeter 300 having an analog sensor 310, adigital data source 320 and a switch 360 connected to a multipurposesensor port 301. If the pulse oximeter 300 reads an ID that identifiesmixed analog and digital, then the multipurpose sensor port 301functions to transfer either an analog signal or digital data, asdetermined by the switch 360. The state of the switch 360 may bedetermined by the data source 320, the pulse oximeter 300 or both. Inone embodiment, the pulse oximeter 300 transmits an identifiablewaveform over an LED drive path 510 (FIG. 5) that is recognized by theswitch 360 as a change state command. In this manner, the pulse oximeter300 may occasionally receive digital data from, or transmit digital datato, the data source 320.

Applications

FIG. 4 illustrates various digital data source 320 and sensor portinterfaces 330 that connect to a multipurpose sensor port 301. In oneapplication, a preprogrammed module 405 connects directly to the sensorport 301. The module 405 has nonvolatile memory preprogrammed with, forexample, upgrade firmware for the pulse oximeter 300. The module 405also has the associated electronics to readout the memory data andcommunicate that data to the sensor port 301. In particular, the module405 provides mechanical, signal level, and communication protocolcompliance with the sensor port 301.

As shown in FIG. 4, in another application, a PC 410 connects to thesensor port 301 via a PC interface 450. For example, the PC 410 can beused to download firmware to the pulse oximeter 300, as described withrespect to FIG. 5, below. As another example, the PC 410 can be used toupload information from the pulse oximeter 300, as described withrespect to FIG. 6, below. In one embodiment, the PC interface 450provides mechanical and signal level compliance with RS-232 on the PCside and mechanical and signal level compliance with the sensor port 301on the pulse oximeter side, as described with respect to FIG. 9, below.

Also shown in FIG. 4, a physiological sensor 420 other than aconventional pulse oximeter sensor is attached to the multipurposesensor port 301. A physiological sensor interface 460 drives thephysiological sensor 420 and generates raw digital data to the sensorport 301. In this manner, a pulse oximeter 300 can be advantageouslyextended to provide physiological measurements in addition to oxygensaturation and pulse rate.

Further shown in FIG. 4, a wireless data device 430 is attached to themultipurpose sensor port 301 via a wireless interface 470. In thismanner, the pulse oximeter can be advantageously extended to wirelessdata I/O and wireless networks. In one embodiment, the wirelessinterface 470 provides mechanical and signal level compliance with awireless standard, such as IEEE-802.11, on one side and mechanical andsignal level compliance with the sensor port 301 on the pulse oximeterside.

Additionally shown in FIG. 4, networked digital I/O devices 440 areattached to the multipurpose sensor port 301 via a network interface480. In one embodiment, the network interface 480 provides mechanicaland signal level compliance with a network standard, such as Ethernet,on one side and mechanical and signal level compliance with the sensorport 301 on the pulse oximeter side.

Firmware Upgrade Port

FIG. 5 illustrates a multipurpose sensor port 301 configured to downloadpulse oximeter firmware 501. The firmware 501 is uploaded to a PC 410and downloaded over a standard communications bus 503 to a target pulseoximeter 300. The standard bus 503 may be, for example, RS-232,IEEE-488, SCSI, IEEE-1394 (FireWire), and USB, to name just a few. A PCinterface 450 translates the signal levels on the sensor port 301 to thesignal levels of the standard bus 503, and vice-a-versa. In particular,an output signal on the standard bus 503 is translated to a sensor portinput signal 522, and a sensor port output signal 512 is translated toan input signal on the standard bus 503.

As shown in FIG. 5, the pulse oximeter 300 has a detector signal path520, a DSP 530, a flash memory 540 or other nonvolatile memory and a LEDdrive path 510, such as described with respect to FIG. 2, above. Datatransmitted from the PC 410 is carried on the sensor port input 522,over the detector signal path 520 to the DSP 530, which loads the datainto a flash memory 540. Acknowledgement data is transmitted from theDSP 530, over the LED drive path 510, and is carried on the sensor portoutput 512.

FIG. 6 illustrates a memory map 600 for the DSP flash memory 540 (FIG.5). The memory map 600 illustrates partitions for DSP executableinstructions such as boot firmware 610, signal processing firmware 620and sensor port communications firmware 630 in addition to applicationdata 640. The boot firmware 610 executes upon DSP power-up. The bootfirmware 610 initializes the DSP and loads either the signal processingfirmware 620 or the communications firmware 630 into DSP program memory,depending on the device ID, as described with respect to FIGS. 3A-D,above. The signal processing firmware 620 contains the oxygen saturationand pulse rate measurement algorithms, referred to with respect to FIGS.1-2, above. The communications firmware 630 contains communicationsprotocol algorithms, such as described with respect to FIG. 8, below.After completing its task of downloading firmware and/or uploading theapplications data 640, the communications firmware 630 loads the signalprocessing firmware 620 so that the DSP can perform pulse oximetrymeasurements.

Also shown in FIG. 6, the application data 640 includes trend data 632,operational logs 634 and manufacturer's logs 638, which can beadvantageously uploaded to a PC 410 (FIG. 5) or other digital deviceconnected to the sensor port 301 (FIG. 5). Trend data 632 containsoxygen saturation and pulse rate measurement history. Operational logs634 contain, for example, failure codes and event information. Failurecodes indicate, for example, pulse oximeter board failures and hostfailures. Event information includes alarm data, such as the occurrenceof probe off and low saturation events. Manufacturer's logs 638contains, for example, service information.

FIG. 7 illustrates a multipurpose sensor port embodiment 301incorporating an LED drive path 510, a detector signal path 520 and aDSP 530, which function generally as described with respect to FIG. 5,above. The LED drive path 510 has a shift register 710, a red LED drive720 and an IR LED drive 730. The shift register 710 has a data input712, a red control output 714 and an IR control output 718. The DSP 530provides serial control data on the shift register input 712 that islatched to the shift register outputs 714, 718 so as to turn on and offthe LED drives 720, 730 according to a predetermined sequence of red on,IR on and dark periods. The detector signal path 520 has a preamp 740,signal conditioning 750 and an ADC 760 that perform amplification,filtering and digitization of the detector signal 522. The detectorsignal path 520 also has a comparator 770 that compares the preampoutput 742 to a fixed voltage level and provides an interrupt output 774to the DSP 530 accordingly. The comparator 770 allows the DSP to controlthe preamp voltage as a function of the level of the preamp signaloutput 742, as described in U.S. patent application Ser. No. 10/351,961entitled “Power Supply Rail Controller,” filed Jan. 24, 2003, which isassigned to Masimo Corporation, Irvine, Calif. and incorporated byreference herein. Advantageously, the comparator signal path also allowsthe DSP to accept serial digital data, as described with respect to FIG.8, below.

FIG. 8 illustrates a serial data receiver 800 embodiment of one aspectof the communications firmware 630 (FIG. 6). The data receiver 800utilizes the detector signal path 520 (FIG. 7) described above. A DSPinternal timer is initialized to generate an interrupt at the incomingdata baud rate. The timer interrupt periodically starts the datareceiver 800 to determine and store a single bit. The data receiver 800polls the status of the DSP interrupt input 774 (FIG. 7), which isinitialized to be level-sensitive and disabled. Thus, whenever thecomparator 770 (FIG. 7) is triggered, it will latch into a DSP interruptpending register but will not generate an interrupt event. The timerservice routine 800 polls the interrupt pending register 820. Thepending register value is determined 830. If the value is a “1,” then azero bit has been received 840, else a one bit has been received 850.The received bit is stored 860 and the timer reset 870.

FIG. 9 illustrates an RS-232 PC interface embodiment 450 having anRS-232 connector 910, a sensor connector 920, a voltage regulator 930and a transceiver 940. The voltage regulator 930 draws power from eitherthe RS-232 910 RTS (request to send) or DTR (data terminal ready) signallines and provides regulated VCC power to transceiver 940. Thetransceiver 940 operates on either of the sensor 920 red or IR drivesignal lines to generate an RS-232 910 RXD (receive data) signal. Thetransceiver 940 further operates on the RS-232 TXD (transmit data)signal line to generate a sensor 920 detector signal.

A multipurpose sensor port has been disclosed in detail in connectionwith various embodiments. These embodiments are disclosed by way ofexamples only and are not to limit the scope of the claims that follow.One of ordinary skill in the art will appreciate many variations andmodifications.

1. A device configured to allow digital communication between a sensorport of a patient monitor and a digital data source external to thepatient monitor, the device communicating over conductors at timestasked with communicating analog drive signals to a sensor andconductors at times tasked with communicating analog signals to thepatient monitor indicative of light detected by said sensor that hasbeen attenuated by body tissue, said device comprising a sensor portinterface configured to provide mechanical and signal level compliancebetween said sensor port and said digital data source, said sensor portdigitally communicating through said sensor port interface with saiddigital data source, said sensor port communicating said analog signalswith said sensor and wherein only one of said sensor or said sensor portinterface can be connected with said sensor port at a time.
 2. Thedevice of claim 1 wherein the interface communicates digital upgradefirmware data to the sensor port.
 3. The device of claim 1 wherein thedigital data source comprises a PC and wherein the sensor port interfaceprovides signal level, mechanical, and communication protocol complianceto the output of the PC.
 4. The device of claim 3 wherein the PCtransmits upgrade firmware to the digital data interface, and whereinthe interface translates the upgrade firmware from a standard PC outputsignal into a sensor port input signal and communicates the sensor inputsignal to the sensor port.
 5. The device of claim 1 wherein the digitaldata source comprises a second physiological sensor and wherein thesensor port interface communicates drive signals to the secondphysiological sensor and wherein the physiological sensor generatesdigital data and transmits the digital data through the sensor portinterface to the sensor port of the physiological measurement system. 6.The device of claim 1 wherein the digital data source comprises awireless data service.
 7. The device of claim 1 wherein the digital datasource employs a network standard in its communication.
 8. A method ofadapting a communication bridge, said bridge between a patientmonitoring device and a physiological sensor the device uses to acquiresignals responsive to physiological parameters of a patient to allow thedevice to determine measurement values for said physiologicalparameters, said bridge accommodating communication between said deviceand a digital data source, the method comprising: providing an interfacemechanically and electrically connectable to a sensor port of thepatient monitoring device, the interface configured to communicate withthe digital data source, wherein the sensor port is also configuredmechanically and electrically connect to a physiological sensorincluding emitters and one or more detectors adapted to detect lightfrom said emitters after attenuation by tissue at a tissue site of saidpatient, said detected light responsive to said parameters of saidpatient; and transmitting digital data between the digital data sourcethrough the interface and to at least some conductors associated withthe sensor port wherein the at least some conductors associated with thesensor port are also used to communicate analog signals to thephysiological sensor and wherein only one of said sensor or said digitaldata source can be connected with said sensor port at a time.
 9. Themethod of claim 8 wherein the digital data further comprises upgradefirmware for upgrading the firmware of the physiological monitor. 10.The method of claim 9 wherein the digital data source comprisesnon-volatile memory storing said upgrade firmware.
 11. The method ofclaim 9 wherein the digital data source comprises a PC storing saidupgrade firmware.
 12. The method of claim 8 wherein the digital datafurther comprises measurement data from said physiological monitor. 13.The method of claim 12 wherein the digital data source comprisesnon-volatile memory storing said measurement data.
 14. The method ofclaim 12 wherein the digital data source comprises a display.
 15. Themethod of claim 12 wherein the display displays indicia responsive tosaid measurement.
 16. The method of claim 8 wherein the digital datasource comprises a PC and wherein the interface provides signal level,mechanical, and communication protocol compliance to the output of thePC.
 17. The method of claim 8 wherein the digital data source comprisesa second physiological sensor and wherein a drive signal is communicatedfrom the at least some conductors associated with the sensor port,through the interface, to the physiological sensor and wherein thephysiological sensor generates raw digital data which is communicatedthrough the interface to the sensor port of the physiological monitor.18. The method of claim 8 wherein the digital data source is compriseswireless data service.
 19. A communication bridge adapted to communicatebetween an analog sensor and a physiological measurement device and alsoadapted to communicate between a digital data source and a physiologicalmeasurement device, said bridge comprising: means for at one timecommunicating digital data between a digital data source and a sensorport of a physiological measurement system; and means for communicatingat another time between the sensor port of a physiological measurementsystem an analog physiological sensor including emitters and detectoradapted to detect light from said emitters after attenuation by tissueat a tissue site of said patient.
 20. The device of claim 19 wherein thedigital data further comprises upgrade firmware.